PYRENOPHORA 247 



tion occurred through the deposition of conidia of the fungus. 

 When the leaves are diseased in the normal manner, I have 

 frequently seen the ear well out of the leaf-sheath, and many 

 or all of the grains presenting a shrivelled appearance, but this 

 shrivelling of the grain I found to be invariably due to the 

 work of T/irips ceralium (Halid). 



By some authors it is considered that the fungus under 

 observation is a biologic species, confined to barley. This 

 idea, however, is by no means correct. During the month 

 of June, 1908, a quantity of barley attacked by Helmintho- 

 sporium was sent to Kew from Norfolk for investigation. 

 With spores obtained from this material I infected a quantity 

 of leaves of Hordeum murinum. 



The leaves were placed on damp blotting-paper in a Petri 

 dish, and within a week were covered with a dense mass of 

 conidia of the Helminthosporium. The material was allowed 

 to become thoroughly dry, when leaves of grasses belonging 

 to the following genera were infected and within five days 

 bore a plentiful crop of conidia Festuca ovina, Briza media, 

 Dactylis glot/ierata, Poa annua, and Ar?-he7iatherum aven- 

 aceum. The last-named grass was attacked most vigorously, 

 and repeated experiments proved that it was a favourite host. 

 No infection followed with the following, Avena fatua, Aira 

 caespitosa, and Holcits lanatus. When the original material 

 was six months old having been kept dry all the time, and 

 at the ordinary temperature of the laboratory, a number of 

 barley grains were dipped in very diluted gum-water, rolled 

 on the spore-mass in the Petri dish, and then sown. Most 

 of the grains thus treated showed the disease on the first 

 leaf; a check lot of the same batch of seed, not infected 

 with conidia, sown at the same time, remained free from 

 disease. Similar results followed a second experiment con- 

 ducted when the spores in the Petri dish were just one year 

 old. These experiments prove that the conidia of Helmin- 

 thosporium, under the conditions stated above, retain their 

 vitality for a year, and furthermore, that when the conidia are 

 sown along with the seed, infection of the seedling takes 

 place, as stated by Ravn. 



Sclerotia-like bodies are formed in the tissues of the leaves, 

 and on the straw, more especially at the nodes. These 

 bodies bear the ascigerous form of fruit the following 

 spring. 



Ascigerous form. Perithecia gregarious, conical, mouth 



